Inlet flow distributor for a heat exchanger

ABSTRACT

To minimize pressure drop and optimize flow distribution, the inlet nozzle of a shell and tube heat exchanger for transferring heat from a liquid metal is disposed in an enlarged portion of the shell and has one or more flow distributors disposed to form an oblique angle with respect to the inlet nozzle and with respect to the tube. The flow distributor cooperates with either a sleeve enwrapping the tubes or a plurality of circular plates having one portion thereof cut away to distribute the incoming fluid evenly to all portions of the tube bundle so that the fluid flows lengthwise along the outer surface of the tubes.

United States Patent Harris INLET FLOW DISTRIBUTOR FOR A HEAT EXCHANGER Inventor:

Assignee: The United States of America as William G. Harris, Tampa, Fla.

represented by the United States Energy Research and Development Administration, Washington DC.

Filed:

Feb. 24, 1972 Appl. No.: 229,000

References Cited UNITED STATES PATENTS Sprague 122/34 Durst et a1. 122/32 X Bernstein et a1.... 165/159 Campbell 165/134 X 1 July 22, 1975 FOREIGN PATENTS OR APPLICATIONS 13,727 6/1913 United Kingdom 165/159 514.948 11/1939 United Kingdom ..-l65/159 Primary E.\-an1inerManue1 A. Antonakas {57] ABSTRACT To minimize pressure drop and optimize flow distribution. the inlet nozzle of a shell and tube heat exchanger for transferring heat from a liquid metal is disposed in an enlarged portion of the shell and has one or more flow distributors disposed to form an oblique angle with respect to the inlet nozzle and with respect to the tube. The flow distributor cooperates with either a sleeve enwrapping the tubes or a plurality of circu1ar plates having one portion thereof cut away to distribute the incoming fluid evenly to all portions of the tube bundle so that the fluid flows lengthwise along the outer surface of the tubes.

3 Claims, 5 Drawing Figures Q 27 E 1 Q Q INLET FLOW DISTRIBUTOR FOR A HEAT EXCHANGER BACKGROUND OF THE INVENTION This invention relates to shell and tube heat exchangers and more particularly to flow distributors for the inlet fluid introduced into the shell side thereof.

' supply of flssionable'material is limited, so that the future of nuclear power generation depends on developing a fast breeder reactor, which produces more fissionable material than it consumes. Such systems require heat exchangers to transfer heat from a primary fluid such as liquid sodium or other liquid metal to a secondary fluid such as water or steam. These heat exchangers often utilize a vertical downward flow path for the liquid metal, wherein the liquid metal is on the shell side of the tubes. Introducing the liquid metal into the side of the shell requires that the inlet liquid undergo a change of direction of at least 90 with a minimum pressure loss and that the horizontal velocities adjacent the tubes be as low as practical to keep the shedding frequencies and the accompanying tube vibrations within acceptable limits, and to keep the interface of the liquid and an inert gas blanket free of turbulence to minimize gas entrapment in the liquid metal.

SUMMARY OF THE INVENTION In general, a heat exchanger, when made in accordance with this invention, has a shell portion and a plurality of tubes disposed lengthwise with respect to the shell. The shell has a head portion adjacent one end thereof, a fluid inlet nozzle adjacent the one end and a flow directing device disposed in the flow path of the fluid between the nozzle and the tubes. The flow directing device is disposed at an oblique angle with respect to the axis of the nozzle and with respect to the axis of the tubes. The flow directing device also cooperates with the shell to cause the fluid introduced through the inlet nozzle to flow lengthwise with respect to the tubes and minimize the resistance to flow while so directing the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of this invention will become more apparent from reading the following detailed descriptions in connection with the accompanying drawings, in which:

FIG. 1 is an elevational view of a shell and tube heat exchanger incorporating this invention;

FIG. 2 is an enlarged partial sectional view showing an embodiment of this invention;

FIG. 3 is an enlarged partial sectional view similar to FIG. 2 showing a modification;

FIG. 4 is an enlarged partial sectional view showing another embodiment of this invention;

FIG. 5 is a sectional view taken on line V-V of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings in detail, FIG. I shows a shell and tube heat exchanger or steam generator I having one or more J-shaped tube bundle modules 3 which are nested in a pot or vessel 5. The tube bundles 7 are disposed in two vertical stems or shell portions 9 or II which extend upwardly from the vessel 5. Primary fluid such as a liquid metal. i.e., liquid sodium. enters the longer stem or shell 9 through a primary fluid inlet nozzle 13 disposed adjacent the upper end thereof and flows downwardly within the shell 9 along the outside of the tubes 7. A primary fluid outlet nozzle 15 is disposed in a lower head or end closure 17 of the vessel 5. Secondary fluid such as water or steam enters a secondary fluid inlet nozzle 19 disposed in a head portion 21 closing the upper end of the short stem 11 and flows bundle and then to a head portion 23 disposed at the upper end of the long stem portion 9 and is discharged through a secondary fluid outlet nozzle 25 disposed in the head portion 23. The secondary fluid thus flows in counterflow relation to the primary fluid and extracts heat therefrom in so doing. The primary fluid inlet 13 is disposed in an enlarged portion 27 of the shell 9 adjacent the upper end thereof.

As shown in FIG. 2 a flow distributor or baffle 29 is disposed in the flow path of the primary fluid entering the primary nozzle 13. A sleeve 31 enwraps the tube bundle 7 and extends a short distance above and below the nozzle 13. The flow distributor 29 is an ellipticalshaped plate with an elliptical central opening disposed to form an oblique angle with respect to the primary fluid inlet nozzle 13 and the tube bundle. The outer pcriphery of the flow distributor 29 is adapted to closely fit the expanded portion 27 of the shell 9 and to be attached to the sleeve 31 by welding or other means. The flow distributor 29 is also so disposed with respect to the inlet nozzles to cause the primary fluid entering therethrough to flow around an annular chamber 33 formed between the sleeve and the shell and downwardly toward the lower end of the expanded portion 27. Sloping sides 34 at the lower end of the expanded portion 27 cooperate with the sleeve 31 and the flow distributor 29 to direct the primary fluid into the tube bundle from all sides and then downwardly or lengthwise along the outside surface of the tubes 7.

An inert gas blanket is maintained in the upper portion of the long stem 9 above the upper edge of the sleeve 31 and a rupture disk 35 is disposed in the stem or shell in the gas space. A baffle or deflector plate 37 is disposed above the primary fluid level and is positioned at an oblique angle with respect to the tube bundle and with respect to the rupture disk 35.

Steel shot 39 fllls the space between the deflector plate 37 and a tube sheet 41 forming an integral portion of the head portion 23.

A liner 43 enwraps the tube bundle 7 in the lower portion of the long shell or stem 9. As shown in FIG. 2 the liner 43 and sleeve 31 are separate and there is a space therebetween for the primary liquid to flow through. However, the sleeve 31 and liner 43 could be made integral and openings could be provided adjacent the sloping walls 34 of the shell 9 to allow the primary fluid to enter the tube bundle from all sides to insure even distribution of the primary fluid to the tube bundle 7.

In the arrangement shown in FIG. 3, the elliptical flow distributor 29 directs the primary fluid upwardly toward the upper end of the sleeve 31. A dish-shaped deflector-45 is disposed above the sleeve and is adapted to prevent the annular upward flow from distu rbing' the interface between the inert gas and the primary fluid. The'deflector 45 also cooperates with the sleeve 31 and flow distributor 29 to turn the flow of primary fluid inwardly and distribute the primary fluid evenly to all portions of the tube bundle 7. An elliptical seal ring is disposed adjacent the peripheral edge of the flow distributor -29 to provide support for the sleeve 31 and prevent the primary fluid from flowing downwardly adjaeent the walls of the shell 9. The flow distributor 29 is also seal welded to the sleeve 31 so that essentially all of the primary fluid will flow upwardly'as it enters the shell 9 through the primary fluid inlet nozzle 13.

The liner 43 may be a continuation of the sleeve 31 or may be a separate cylinder depending therefrom.

The arrangements shown in FIGS. 2 and 3 each advantageously provide an open relief path to release the pressure build-up which would result from a reaction between the primary and secondary fluid, i.e. the pressure build-up resulting from the gaseous products produced by areaction between sodium and water.

As shown in FIG. 4, the enlarged portion"'49 of the shell 9 may be eccentric rather than concentric with respect to the shell. If such an arrangement is utilized, the primary'fluid inlet nozzle 13 is so disposed as to be the maximum distance from'the tube bundle 7. A plurality of flow distributors or flatplatesSl are disposed at an oblique angle with respect to the primary fluid inlet 13 and the tube bundle 7. The distributor plates 51 are so disposed with respect to each other as to generally diverge as the distance from the inlet nozzle 13 increases. Each distributor plate 51 is cooperatively associated with a generally circular plate 53 through whichthe tubes pass. Each circular plate 53 has a portion thereof cut awayfThe lowest plate has the greatest portion cut away so that it is cresent-shaped. Successively higher circular plates have a smaller portion cut 'away so that the primary'fluid is directed to differentiportions of the tube-bundle. The cut away edges of the circular plates -,-40

scribed. thus'clooperate with thesleeve 31 or circular plates 53 to change the direction of the flow of primary vide a minimum resistant flow path; they keep horizontal components of the flow velocity low to keep shedding frequencies and the accompanying tube vibration, within acceptable limits; and they help maintain an undisturbed interface surface between the primary fluid and the inert gas blanket to minimizejthe entrainment of inert gas into primary fluid. i

What is claimed'is:

l.' A heat exchanger having'a shell portion. a plurality of tubes disposed lengthwise within'said shell, to form a tube bundle, said shell having a head portion adjacent one end thereof, a fluid inlet nozzle adjacent said one end, a portion of theshell containing sa'idirilet nozzle having a greater diameter than the remainder of the shell and being eccentrically disposed with respect to the remainder of the sehll, the inlet nozzle being so disposed in the greater diameter portion to maximize the distance between thef inlet nozzle and the tubes, and flow directing means disposed in the flow path between said nozzle and saidt ubes, said flow directing means comprises a plurality of flat plates disposed at an oblique angle with respect to the axis of the inlet nozzle and with respect to the axis of the tube bundle, the flat plates being so disposed as to generally diverge as-the distance from the inlet nozzle increases, each of said plates being coopertively associated with a generally circular plate through which the tubes pass, each circular plate having a portion thereof cut away to direct fluid flowing from said inlet nozzle to a different portion of the tube bundle and lengthwise alongthe outside of the tubes, thereby minimizing the flow resistance of the fluid while so directing the flow.

2. A heat exchanger as set forth in claim 1, wherein the flat plates are separated from the circular plates to allow the circular plates to move with the tubes as the tubes dmove lengthwise. due to thermal expansion thereof.

3. A heat exchanger as set forth in claim 1, wherein the circular plates have ,a lip adjacent the edge formed by cutting away a portion thereof, the lip being disposed to cooperate with the circular plate downstream thereof to direct the fluid lengthwise along the outisde of the tubes.

' k I i 

1. A heat exchanger having a shell portion, a plurality of tubes disposed lengthwise within said shell, to form a tube bundle, said shell having a head portion adjacent one end thereof, a fluid inlet nozzle adjacent said one end, a portion of the shell containing said inlet nozzle having a greater diameter than the remainder of the shell and being eccentrically disposed with respect to the remainder of the sehll, the inlet nozzle being so disposed in the greater diameter portion to maximize the distance between the inlet nozzle and the tubes, and flow directing means disposed in the flow path between said nozzle and said tubes, said flow directing means comprises a plurality of flat plates disposed at aN oblique angle with respect to the axis of the inlet nozzle and with respect to the axis of the tube bundle, the flat plates being so disposed as to generally diverge as the distance from the inlet nozzle increases, each of said plates being coopertively associated with a generally circular plate through which the tubes pass, each circular plate having a portion thereof cut away to direct fluid flowing from said inlet nozzle to a different portion of the tube bundle and lengthwise along the outside of the tubes, thereby minimizing the flow resistance of the fluid while so directing the flow.
 2. A heat exchanger as set forth in claim 1, wherein the flat plates are separated from the circular plates to allow the circular plates to move with the tubes as the tubes move lengthwise due to thermal expansion thereof.
 3. A heat exchanger as set forth in claim 1, wherein the circular plates have a lip adjacent the edge formed by cutting away a portion thereof, the lip being disposed to cooperate with the circular plate downstream thereof to direct the fluid lengthwise along the outisde of the tubes. 